This invention relates to a braking mechanism for a linear induction motor, and more particularly, the invention relates to a fail-safe mechanism formed integrally with the motor which automatically stops the motor armature when electric current ceases flowing through the motor.
Linear motors of the type including a movable member or armature which is caused to move perpendicularly through a gap between a plurality of fixed stators, or stators and fixed cooperating magnetic return path members, have heretofore been widely known and used. This type of linear motor has one disadvantage in that the armature is free to move in an axial direction when the motor is not energized, i.e., when there is an absence of magnetic flux across the gap. While the armature in a conventinal curvilinear electric motor is free to rotate when it is not energized, the free transitory motion available to the armature in a linear motor in certain instances poses more substantial problems than does the freedom to rotate of a conventional motor.
Heretofore, braking mechanisms for linear induction motors have been operated by a system which is independent of the motor circuit. These braking mechanisms have been utilized in connection with one common application of the linear induction motor which is as a driving part of a monorail transportation system. U.S. Pat. Nos. 3,198,138 and 3,618,529 disclose hydraulically or pneumatically operated brake pad members in a linear motor which frictionally bind the movable motor member (monorail) to the stationary motor members. Both of the systems are operated by systems independent of the motor circuit. In U.S. Pat. No. 3,356,041, electrical pole-switching is utilized to obtain a reverse thrust for braking on a monorail transportation system.
A need has arisen for a simple braking mechanism which secures the armature of a linear induction motor in a stationary position, as desired. An additional need exists for a fail-safe type of brake mechanism in a linear induction motor.